At 9pm today, police dispersed mourners at Times Square in Causeway Bay who were commemorating the 1989 Tiananmen crackdown.
Thirty minutes later, a woman was taken away by police officers.
After nightfall, members of the public were seen holding candle lights or turning on their mobile phone flashlight on the streets of Causeway Bay, remembering the victims of the crackdown.
Police released a statement online at around 9.30pm today, warning people in Causeway Bay to stop throwing objects onto roads to block traffic.
The statement wrote there were black-clad protestors gathering in the vicinity of Percival Street in Causeway Bay, with some throwing objects onto roads.
It warned that the force will take out law enforcement actions when necessary.